"While silicon carbide is strong in abrasion and compression applications, it does not have the same strength against expansion and shear forces. Some fission products such as xenon-133 have a limited absorbance in carbon, and some fuel kernels could accumulate enough gas to rupture the silicon carbide layer.[citation needed] Even a cracked pebble will not burn without oxygen, but the fuel pebble may not be rotated out and inspected for months, leaving a window of vulnerability."

So how many cracked pebbles are allowed in the PBR?

So, when Air gets in there, how many burning pebbles are allowed?

Also given the general pressure on Helium supplies, is there enough helium production?

it is the contention of the author that the Fukushima plants handled a very serious challenge well. John gets apopleptic when I propose that it was bad engineering and unethical engineering to not design for an "Inconceivable" earthquake.

Well Let's look. Fukushima is in Northern Japan, it's on the Tohuko Plain, just a tad north

of a place called Iwate. http://en.wikipedia.org/wiki/1896_Meiji-Sanriku_earthquake

in 1896, a mere 7 decades before the Fukushima Reactors were built, the Meiji-Sanriku quake a mere baby at 8.5 released 38 Meter tsunami. For Comparison in 2011, the Tohuko quake releases a 39 Meter tsunami.

The SeaWall at Fukushima was 6 Meters tall.

Japan is the nation with the most recorded tsunamis in the world.[citation needed] The number of tsunamis in Japan totals 195 over a 1,313 year period (thru 1997), averaging one event every 6.73 years, the highest rate of occurrence in the world.[citation needed]

So a phenomena that occurs on average every 6 years and has helped define Japanese culture, and just a little ways down the road, and within the lifetime of nearby residents a 38 meter tsunami rolls in.

But, when I mention it was a breach of ethics, John goes Berserk. Name calling, whinging, really very unbecoming.

I'll ask a very specific question for John

1A) How high should the seawall at Fukushima have been?

1B) How powerful of an earthquake should the site have been hardened for?

Lets see if the Name Calling continues, or if a Engineering based Numerical Answer is given.

What wasn't easy and safe in the 1960's, is significantly different in 2013.

It's much easier today to use multiple containments at that temp, all of which are Helium flooded. Ceramic coating the pebbles would also seal off the carbon moderator, even with O2 present. With O2 blocked from the carbon moderator, they simply do not burn.

With the entire system at low pressure and no phase transistions available, explosions and fire are simply not an option, as with water moderated systems. AND no active control/cooling system is required, OR wanted.

That completely avoids the Fukushima failure problems and the TMI failure problems

The most common criticism of pebble bed reactors is that encasing the fuel in combustible graphite poses a hazard. When the graphite burns, fuel material could potentially be carried away in smoke from the fire.

So lets See, Windscale and chernobyl were both Graphite reactor fires.

All it takes is a stuck valve, busted pipe, operator error, and that 1600 F carbon bursts into flame.

I can just feel the safety.

The point of water moderated reactors was to eliminate the risks of carbon reactors.

"On February 2, 1976, Gregory C. Minor, Richard B. Hubbard, and Dale G. Bridenbaugh "blew the whistle" on safety problems atnuclear power plants. The three engineers gained the attention of journalists and their disclosures about the threats of nuclear power had a significant impact. They timed their statements to coincide with their resignations from responsible positions in General Electric's nuclear energy division,

,,,,

Following the 2011 Tōhoku earthquake and tsunami that devastated northern Japan, a series of explosions and a containment failure at the Fukushima I Nuclear Power Plant resulted in media coverage of the GE Three. Bridenbaugh described design flaws of General Electric's Mark 1 reactors, which account for five of the six reactors at the Fukushima 1 power plant. Bridenbaugh claimed that the design "did not take into account the dynamic loads that could be experienced with a loss of coolant" and that, despite efforts to retrofit the reactors, "the Mark 1 is still a little more susceptible to an accident that would result in a loss of containment."[3]"

"The problems we identified in 1975 were that, in doing the design of the containment, they did not take into account the dynamic loads that could be experienced with a loss of coolant," Bridenbaugh told ABC News in an interview. "The impact loads the containment would receive by this very rapid release of energy could tear the containment apart and create an uncontrolled release.""

http://rpsd.ans.org/ethics3.pdf

 The nuclear enterprise is a societal good◦ The nuclear industry has adequate skills and technology to succeed. ◦ If we fail it will mostly likely be by ethical lapses.

So if we listen to the GE 3, the Mark 1 design was doomed to fail, and as we saw, the first time the containment was presented with a core meltdown, the containments in units 1-3 failed.

if we listen to Robert Wilson, the Industry has adequate skills and technology but failure will be by ethical lapses.

Well, What can I say?

John is out there howling, but, he's not a nuclear engineer. The reality is that when faced with a predictable design challenge, 4 nuclear reactors exploded. I don't have to be a nuclear engineer to say that.

I suppose Econazi publications like DesignNews should be utterly ignored when they print stories like http://www.designnews.com/author.asp?section_id=1392&doc_id=263150&itc=dn_analysis_element&

To put this in context, on the most recent record-setting day for wind power, total energy demand on the system peaked at 4:07 p.m. with 27,426 megawatts. During the preceding hour, the system got 28.8 percent of its generated power from renewables, including wind, solar, biogas, biomass, small-scale hydroelectric power, and geothermal. That's not too far off from the 33 percent set by the California Renewables Portfolio Standard (RPS) as the proportion of energy that must be generated from renewable sources by 2020.

&

Most of the new energy capacity the ISO expects to be generated in California during 2H 2013, about 97 percent, will be from solar, according to the report. During 2012, most of the growth in renewables was due to increases in wind and solar resources. Energy from new solar and wind capacity during 2013 is expected to increase much faster than from other sources

Damn these Eco-Nazis, making so many people in California Suffer. All the people freezing, starving, dying. The babies being eaten by the ravenous hordes.

Oh the Humanity, if only we had some wonderful person like John to save us from all this terrible cheap Wind and solar energy.

Will Some Hero, like John, just start bombing Windmills to save the birds from the rotors of death, and pound the rotors into pressure vessels.

And by the way .... PatB doesn't seem to be a nuke plant engineer, but in his first post on "4/26/2013 1:47:41 PM" he sets the tone that I've considered fair game in this series.

It's absolutely being a jack a** to claim the engineers designing the plant completely lacked any ethics .... his quote is "Any designer who fails to look at the 100 year environment when designing civil protection systems, is failing to meet the canons of ethics, IMHO."

the other quote ending the same piece is: "Competent designers should be ashamed of how the fukushima reactors performed."

It's one thing to be an expert in the field, and know with first hand experience of participating in the design meetings for that plant, that the engineers failed to meet or better the design requirements forced on them by the government regulators and executives. So far, it seems they did meet or better the requirements set for them. It's clear in retrospected, that things could have been better ... every project has that problem with hindsight. Problems start with poor regulations, specifications and budgets.

It's another thing to be a jack a**, without any credientials and experience in the field, and spout off with such attacks against the engineers involved, without understanding the resource limits placed on them by regulators and executives.

Frankly, every anti-nuke protester, should be ashamed at blocking a clean alternative, that has caused hundreds of millions to die or suffer from fossil fuel polution related illnesses.

If the companies hadn't lost billions fighting idealogical nuke free world zone court battles, maybe they would have had a LOT more money to put toward safety improvements.

It's pretty shitty to crow about how much money the court battles have cost nuke power facilities, and then completely deny responsibilty for leaving the industry short of cash for upgrades. Anti-nuke protesters need to take responsibility for the deaths they have caused, or contributed to.

It's pretty shitty for PatB to attack the engineers on this project this way, so he can not complain about the tone HE set for this discussion. If PatB lacks the ethics and civility not to call the hundreds of engineers on that project incompentant, then he's being a little thin skined about being called a troll (which his nuke free zone posts are), a nazi (for his lack of appreciation for others views), and a baby killer (for blocking clean nuke power production).

Maybe if the anti-nuke protesters had spent the litigation money to hire good engineers to lobby and improve the regulations, that the failures would have not happened. Instead they just pissed away much needed money for safety, in the courts. Maybe the protesters need to start considering their lack of ethics in killing all the babies, kids, and adults. Maybe the protesters need to be competent constructive citizens building up a safe pollutant free world.

Instead they are patting themselves on the back for killing babies with pollution, stealing money needed for plant safey, and being nazi's for a nuke free world.

I share your admiration for Kennedy, Amclaussen. I don't believe nuclear is safe, it just looks like the alternatives are more dangerous. As for Chernobyl, it had notoriously poor safeguards, an unfortunate result of a political power structure that didn't have to answer to its citizens.

A few weeks ago, Ford Motor Co. quietly announced that it was rolling out a new wrinkle to the powerful safety feature called stability control, adding even more lifesaving potential to a technology that has already been very successful.

It won't be too much longer and hardware design, as we used to know it, will be remembered alongside the slide rule and the Karnaugh map. You will need to move beyond those familiar bits and bytes into the new world of software centric design.

People who want to take advantage of solar energy in their homes no longer need to install a bolt-on solar-panel system atop their houses -- they can integrate solar-energy-harvesting shingles directing into an existing or new roof instead.

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